Configuring the MAC Address Table
Note 
For information about creating interfaces, see the document,
Cisco Nexus 1000V Interface Configuration Guide, Release 4.2(1)SV1(4).
This chapter includes the following topics:
•Information About the MAC Address Table
•Configuring the MAC Address Table
•Example Configuration for the MAC Address Table
•Feature History for the MAC Address Table
Information About the MAC Address Table
Layer 2 ports correlate the MAC address on a packet with the Layer 2 port information for that packet using the MAC address table. A MAC address table is built using the MAC source addresses of the frames received. When a frame is received for a MAC destination address not listed in the address table, the frame is flooded to all LAN ports of the same VLAN with the exception of the port that received the frame. When the destination station replies, the relevant MAC source addresses and port IDs are added to the address table. Then subsequent frames are forwarded to a single LAN port without flooding all LAN ports.
You can configure MAC addresses, which are called static MAC addresses, to statically point to specified interfaces on the device. These static MAC addresses override any dynamically learned MAC addresses on those interfaces. You cannot configure broadcast or multicast addresses as static MAC addresses. The static MAC entries are retained across reboots.
The address table per VEM can store up to 32000 MAC entries. An aging timer triggers removal of addresses from the table when they remain inactive for the default time of 300 secs. The aging timer can be configured on a global basis but not per VLAN.
You can configure the length of time an entry remains in the MAC address table, clearing the table, and so forth.
Guidelines and Limitations
Keep in mind the following guidelines for configuring MAC addresses:
•The forwarding table for each VLAN in a VEM can store up to 4094 MAC addresses.
•The Cisco NX-OS software explicitly prohibits configuring port security on ports that have a static MAC addresses configured on the following VLANs:
–the access VLAN of an access port
–the native VLAN of a trunk port
Default Settings
Table 2-1 lists the default setting for the MAC address aging time.
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|---|---|
Aging time |
300 seconds |
Configuring the MAC Address Table
This section includes the following procedures for configuring the MAC address table:
•Configuring a Static MAC Address
•Clearing Dynamic Addresses from the MAC Address Table
Configuring a Static MAC Address
Use this procedure to configure a MAC address to statically point to a specific interface.
BEFORE YOU BEGIN
Before beginning this procedure, you must know or do the following:
•You are logged in to the CLI in EXEC mode.
•You cannot configure broadcast or multicast addresses as static MAC addresses.
•Static MAC addresses override dynamically-learned MAC addresses on an interface.
Note Be aware that the Cisco NX-OS commands may differ from those used in Cisco IOS.
SUMMARY STEPS
1. config t
2. mac address-table static mac address vlan vlan-id {[drop | interface {type if_id | port-channel id]}
mac address-table static mac-address vlan vlan-id {interface {interface-name}+ | drop} [auto-learn]
no mac address-table static mac-address vlan vlan-id
3. show mac address static interface [type if_id]
4. copy running-config startup-config
DETAILED STEPS
Example:
n1000v# config t
n1000v(config)# mac address static
n1000v(config)# show mac address static
VLAN MAC Address Type Age Port Module
---------+-----------------+-------+---------+------------------------------+---------
1 0002.3d11.5502 static 0 N1KV Internal Port 3
1 0002.3d21.5500 static 0 N1KV Internal Port 3
1 0002.3d21.5502 static 0 N1KV Internal Port 3
1 0002.3d31.5502 static 0 N1KV Internal Port 3
1 0002.3d41.5502 static 0 N1KV Internal Port 3
1 0002.3d61.5500 static 0 N1KV Internal Port 3
1 0002.3d61.5502 static 0 N1KV Internal Port 3
1 0002.3d81.5502 static 0 N1KV Internal Port 3
3 12ab.47dd.ff89 static 0 Eth3/3 3
342 0002.3d41.5502 static 0 N1KV Internal Port 3
343 0002.3d21.5502 static 0 N1KV Internal Port 3
Total MAC Addresses: 11
n1000v(config)# show mac address static interface Ethernet 3/3
VLAN MAC Address Type Age Port Module
---------+-----------------+-------+---------+------------------------------+---------
3 12ab.47dd.ff89 static 0 Eth3/3 3
Total MAC Addresses: 1
n1000v(config)#
Configuring the Aging Time
Use this procedure to configure the amount of time that packet source MAC addresses, and the ports on which they are learned, remain in the MAC table containing the Layer 2 information.
Note Although it is a global setting, you can also configure MAC aging time in interface configuration mode or VLAN configuration mode.
BEFORE YOU BEGIN
Before beginning this procedure, you must know or do the following:
•You are logged in to the CLI in EXEC mode.
•The aging time is a global setting that cannot be configured per VLAN.
Note Be aware that the Cisco NX-OS commands may differ from those used in Cisco IOS.
SUMMARY STEPS
1. config t
2. mac address-table aging-time seconds
3. show mac address-table
4. copy running-config startup-config
DETAILED STEPS
Example:
n1000v# config t
n1000v(config)# mac address-table aging-time 600
n1000v(config)#
Clearing Dynamic Addresses from the MAC Address Table
Use this procedure to clear dynamic Layer 2 entries from the MAC address table.
BEFORE YOU BEGIN
Before beginning this procedure, you must know or do the following:
•You are logged in to the CLI in EXEC mode.
Note Be aware that the Cisco NX-OS commands may differ from those used in Cisco IOS.
SUMMARY STEPS
1. clear mac address-table dynamic [vlan vlan_id]
2. show mac address-table
DETAILED STEPS
Verifying the Configuration
Use the following commands to verify the Layer 2 MAC address configuration.
|
|
|
|---|---|
show mac address-table |
Displays the MAC address table. See Example 2-1 |
show mac address-table static |
Displays information about the MAC address table static entries. |
show mac address-table static | inc veth |
Displays the static MAC address of vEthernet interfaces in case a VEM physical port learns a dynamic MAC and the packet source is in another VEM on the same VSM. See Example 2-2 |
show mac address static interface [type if_id] |
Displays all static MAC addresses. See: |
show mac address-table aging-time |
Displays the aging time in the MAC address table. See Example 2-5 |
show mac address-table count |
Displays a count of MAC address entries. See Example 2-6 |
show interface interface_id mac |
Displays the MAC addresses and the burn-in MAC address for an interface. |
Example 2-1 show mac address-table
n1000v# show mac address-table
VLAN MAC Address Type Age Port Module
---------+-----------------+-------+---------+------------------------------+---------
1 0002.3d11.5502 static 0 N1KV Internal Port 3
1 0002.3d21.5500 static 0 N1KV Internal Port 3
1 0002.3d21.5502 static 0 N1KV Internal Port 3
1 0002.3d31.5502 static 0 N1KV Internal Port 3
1 0002.3d41.5502 static 0 N1KV Internal Port 3
1 0002.3d61.5500 static 0 N1KV Internal Port 3
1 0002.3d61.5502 static 0 N1KV Internal Port 3
1 0002.3d81.5502 static 0 N1KV Internal Port 3
3 12ab.47dd.ff89 static 0 Eth3/3 3
342 0002.3d41.5502 static 0 N1KV Internal Port 3
342 0050.568d.5a3f dynamic 0 Eth3/3 3
343 0002.3d21.5502 static 0 N1KV Internal Port 3
343 0050.568d.2aa0 dynamic 9 Eth3/3 3
Total MAC Addresses: 13
n1000v#
Example 2-2 show mac address-table static | inc veth
n1000v# show mac address-table static | inc veth
460 0050.5678.ed16 static 0 Veth2 3
460 0050.567b.1864 static 0 Veth1 4
n1000v#
Example 2-3 show mac address static
n1000v(config)# show mac address static
VLAN MAC Address Type Age Port Module
---------+-----------------+-------+---------+------------------------------+---------
1 0002.3d11.5502 static 0 N1KV Internal Port 3
1 0002.3d21.5500 static 0 N1KV Internal Port 3
1 0002.3d21.5502 static 0 N1KV Internal Port 3
1 0002.3d31.5502 static 0 N1KV Internal Port 3
1 0002.3d41.5502 static 0 N1KV Internal Port 3
1 0002.3d61.5500 static 0 N1KV Internal Port 3
1 0002.3d61.5502 static 0 N1KV Internal Port 3
1 0002.3d81.5502 static 0 N1KV Internal Port 3
3 12ab.47dd.ff89 static 0 Eth3/3 3
342 0002.3d41.5502 static 0 N1KV Internal Port 3
343 0002.3d21.5502 static 0 N1KV Internal Port 3
Total MAC Addresses: 11
n1000v(config)# show mac address static interface Ethernet 3/3
VLAN MAC Address Type Age Port Module
---------+-----------------+-------+---------+------------------------------+---------
3 12ab.47dd.ff89 static 0 Eth3/3 3
Total MAC Addresses: 1
Example 2-4 show mac address static interface
n1000v# show mac address static interface Ethernet 3/3
VLAN MAC Address Type Age Port Module
---------+-----------------+-------+---------+------------------------------+---------
3 12ab.47dd.ff89 static 0 Eth3/3 3
Total MAC Addresses: 1
n1000v#
Example 2-5 show mac address-table aging-time
n1000v# show mac address-table aging-time
Vlan Aging Time
----- ----------
101 300
100 300
1 300
n1000v#
Example 2-6 show mac address-table count
n1000v)# show mac address-table count static
Total MAC Addresses: 12
n1000v#
Example Configuration for the MAC Address Table
The following example shows how to add a static MAC address and establish a global aging time:
n1000v# configure terminal
n1000v(config)# mac address-table static 0000.0000.1234 vlan 10 interface ethernet 2/15
n1000v(config)# mac address-table aging-time 120
Additional References
For additional information related to implementing Layer 2 switching, see the following sections:
Related Documents
Standards
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|---|---|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
— |
Feature History for the MAC Address Table
This section provides the MAC address table release history.
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|---|---|---|
MAC Address Tables |
4.0(4)SV1(1) |
This feature was introduced. |
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